We studied human T cell activation and regulation in the system of continued cultures of T cells that respond to T cell growth factor (TCGF). We studied the TCGF producing cell and cells responding to TCGF by means of anti-T cell sera, and the role of monocytes and serum proteins in T cell activation. Cultured T cells maintained various functions, such as antibody-dependent cell-mediated cytotoxicity, natural cytotoxicity and specific immune cytolysis. CTC were cytotoxic against of human cell lines, as well as fresh lung and breast tumors. The plan is to further dissect the heterogeneity, activation and regulation of human T cells; in the long range, to derive T cells reactive specifically with tumor-associated antigens in leukemias, breast cancer and lung cancer.